Desktop computer use on E2B and Daytona sandboxes

Agents can now operate a full Linux desktop instead of only a browser page. The
experimental computer_use_desktop capability runs the provider-neutral
computer tool on an E2B desktop sandbox, and computer_use_daytona runs it on
a Daytona sandbox through Daytona’s Computer Use API. The session creates the
desktop on first use, keeps it between calls and deletes it when its lease ends.
The computer tool also gained zoom, cursor position, mouse button down and up,
hold-key and modified drag actions on Daytona, E2B and Browserless.
Connect E2B or Daytona first, then add one computer-use capability to the agent;
only one can provide the computer tool.
See Computer use and #4244, #4365, #4367.